We shall continue to investigate the actions of follicle stimulating hormone (FSH) and testosterone on Sertoli cells prepared from testes at various stages of maturation; to determine the nature of products of Sertoli cells in culture; and to investigate which Sertoli cell products are of importance in germinal cell development. We shall determine rates of sugar transport and metabolism by Sertoli cells, and the influences of FSH, insulin and other regulatory agents on these processes. We shall examine the turnover of membrane phospholipids, particularly phoshatidyl inositol, in stimulated and basal Sertoli cells in culture. We shall investigate surface proteins in Sertoli cells which are released into the culture medium. We shall attempt to find a suitable in vitro assay for mammalian germinal cell development.